This invention relates to improvements in apparatus for open-end spinning textile yarns and more particularly to the fibre-opening zone of such apparatus in which a sliver supplied thereto is subjected to an opening operation.
In one known method of open-end spinning a sliver is forwarded to a rotating opening roller provided with needles or saw-tooth type teeth projecting from a peripheral surface thereof so as to separate and open the fibres from the sliver. The fibres are then conveyed on the peripheral surface of the opening roller to the entrance of a fibre feed duct through which they are transported to the inside of a spinning rotor.
The opening roller is mounted for rotation in a circular recess formed in a housing. The recess has a diameter slightly larger than the diameter of the opening roller when measured over the tips of the needles or saw-tooth type teeth. The peripheral surface of the opening roller is normally cylindrical in form and defines with the parallel adjacent surface of the recess and with the inner surfaces of lateral flanges, which are normally provided at each side thereof, a fibre conveying passage of rectangular cross-section. Such arrangements are disclosed in U.S. Pat. No. 3,828,539 and U.S. Pat. No. 4,058,965.
In operation, it has been found that a fibre-conveying passage of rectangular cross-sectional shape does not provide the optimum fibre opening conditions. In particular, it has been found that the fibrous material tends to transfer from the fibre-conveying passage over the flanges into the lateral clearances between the side surfaces of the opening roller and the adjacent surfaces of the housing. Accumulation of fibrous material in these clearances can become so acute as to impair rotation of the opening roller with consequent danger of damage to the opening roller components and interruption of the spinning process.
In U.S. Pat. No. 3,750,382 there is disclosed an opening system in which the supply sliver is opened by a first opening roller and then further opened by a second opening roller. In FIG. 10 various forms of the opening roller peripheral surface and the adjacent recess surface combine to provide different shapes of the fibre conveying passage. In FIGS. 10c and 10d the radial distances between the opening roller peripheral surfaces and the adjacent recess surfaces are greater at the mid-points than at the sides. Each of the tips of the fibre opening teeth protrude from the peripheral surface by equal amounts. Such arrangements have been devised to overcome an excessive combing action tending to damage the fibres which, according to the specification, had been experienced with fibre conveying passages of rectangular shape.
Such arrangements, however, would not provide a satisfactory fibre opening operation. The wide, varying, radial gap between the tips of the teeth and the recess surface results in insufficient opening of the fibrous material, since the fibres tend to accumulate against the recess surface due to centrifugal forces without being acted upon by the teeth. In these circumstances the fibres tend to be rolled into ball-like masses of fibres which will disrupt the spinning process, or at least detrimentally affect the yarn properties, if they reach the fibre collecting surface. Furthermore, because of the lack of fibre control in this known arrangement the problem of transfer of fibres from the fibre conveying passage to the sides of the opening roller would not be overcome.
A similar arrangement is disclosed in Japanese Patent Publication No. 75-35138 which is alleged to overcome the problem of damage to the fibres. However, all the aforementioned disadvantages will also be encountered with this arrangement, thus rendering it unsatisfactory.